1. Field of the Invention
The present invention relates to a device simulation method, device simulation system, and device simulation program for calculating a movable electric charge density inside a semiconductor device, ionization rate of an impurity injected into the semiconductor device, a band gap narrowing and an energy band gap.
2. Related Background Art
With miniaturization of a semiconductor device, a decrease of an energy band of a semiconductor, that is, a so-called band gap narrowing (BGN), and a change of ionization rate of an impurity have had a large influence on an element property. A physical model for reproducing experiment data of the BGN in a numerical calculating manner has been already proposed. However, these models cannot deal with a simulation in case that the devise in which the current flows is ON. The reason is that a conventional BGN model is configured irrespective of external factors such as a current and a potential that modulate inside the semiconductor, and it is principally possible to calculate neither the BGN nor the ionization rate of the impurity in a non-equilibrium state in which the current flows inside the semiconductor.
Moreover, when trying to simultaneously calculate the ionization rate and the BGN, any artifice for enhancing convergence, which has been used in a conventional device simulator, such as adjustment of a control coefficient does not become valid.
Such a situation was not assumed heretofore. The physical model for calculating the BGN has been devised to reproduce the experimented data of the BGN in disregard for non-equilibrium of the ionization rate of the impurity. Therefore, the BGN or the ionization rate of the impurity inside the semiconductor cannot be calculated in any self-consistent manner in accordance with the current or the potential inside the semiconductor.
A technique is necessary for device simulation for a next-generation circuit to calculate not only the BGN and the ionization rate of the impurity in a self consistent manner but also a transport equation of movable electric charge and a Poisson equation, by setting the current and potential given from the electrode of the semiconductor device as boundary conditions.